Author Topic: HP 3456A problem  (Read 2025 times)

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Offline Harvs

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HP 3456A problem
« on: May 17, 2013, 08:05:11 am »
I've got a 3456A that I think has a problem, trying to measure a resistance above about 100k is a hopeless exercise.

The 3 least significant digits oscillate at about 1Hz. It gets worse the higher the resistance measured, with a 10M resistor it can't hold a value within 1% It also does this to a lesser degree on the voltage ranges.

I always figured it was just something I was doing wrong.  But I figure if I get a 500k 1% metal film resistor, and clamp it directly into the screw down binding posts, I should reasonably expect that I would make that measurement, or is there something stupid I'm missing here? 

I remember a thread maybe a year or two back (I can't find it now) which I think Vincent was talking about some caps in them always going bad over time.  So I was thinking maybe there's some power supply ripple getting through and putting things out of whack?

 

Offline mikes

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Re: HP 3456A problem
« Reply #1 on: May 17, 2013, 10:44:35 am »
Are you setting it to 100 PLC, and filter on to reduce noise in the measurement?
 

Offline Harvs

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Re: HP 3456A problem
« Reply #2 on: May 17, 2013, 12:00:54 pm »
Are you setting it to 100 PLC, and filter on to reduce noise in the measurement?

Yep, instability in measurement is still there.

My Escort 3146A 5 1/2 digit is solid as a rock measuring the same things, and it should be the lesser meter as I see it.
 

Offline saturation

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Re: HP 3456A problem
« Reply #3 on: May 17, 2013, 05:44:47 pm »
I have 3 of these, no issues measuring ohms to any range.  Have you run a self diagnostic on the 3456a?
Best Wishes,

 Saturation
 

Offline Harvs

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Re: HP 3456A problem
« Reply #4 on: May 18, 2013, 12:44:22 am »
Yeah don't show anything on the self test.

Thanks for that vital piece of info, that yours don't do it.  Leads me to a more certain conclusion that there is something a miss.

I'll crack the lid and measure some voltages.
 


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